1. Field of the Invention
This invention concerns improvements in and relating to item monitoring, particularly but not exclusively to the monitoring of alpha contamination on large items.
2. Present State of the Art
Direct monitoring of the alpha contamination is only possible using detectors presented very close to the actual source of the alpha particles due to their limited range. Techniques have been developed whereby the ions generated by the passage of alpha particles through air can be detected at long range so as to evaluate the alpha contamination present.
Systems using the principal of long range alpha detection have been developed whereby air is drawn through a filter into a chamber, passes the item under investigation, passes on to a detection unit and subsequently exits the apparatus through an outlet filter. Such systems are relatively complicated as filtration of the feed air is necessary to avoid the introduction of ions from the ambient environment into the chamber and filtration of the outlet flow is necessary to avoid contamination being spread from the item into the environment.